Folding knife



FIG. 1 is a front elevation view of a folding knife showing my new design;

FIG. 2 is a rear elevation view thereof;

FIG. 3 is a top plan view thereof;

FIG. 4 is a left side elevation view of FIG. 1; and,

FIG. 5 is a perspective view thereof. 

CLAIM I claim the ornamental design for a folding knife, as shown and described. 